1. Field of the Invention
This invention pertains to a method and apparatus for making paint rollers of the type used for applying paint to walls and the like.
2. Prior Art
Paint rollers are widely used by professionals and amateurs for applying paint to walls, ceilings, and other surfaces. Typically the roller is used with an applicator having a handle terminating in a rotatable member to which the roller is secured. The roller itself comprises two main components, a core and a paint absorbing cover. The core is typically paper or plastic, while the cover may be wool, polyester, etc. Generally speaking, the methods used for forming the core and for securing the cover to the core determine whether the roller is reusable, as paint solvents such as turpentine, mineral spirits, etc. are also solvents for many adhesives.
To speed production and reduce costs, paint rollers are manufactured using an automated assembly line. For example, according to one known technique, a disposable roller is made by first feeding three chipboard paper strips at an angle to a mandril for overlapping, helical winding to form an endless, belt driven core. The paper strips are supplied in rolls for mounting on spindles for continuous feeding, and a continuous adhesive stream is applied to the outer surfaces of the strips as they feed off the rollers such that the strips adhere together as they are helically wound to form the core. Because the roller is intended as a throwaway, the adhesive is not critical, and an inexpensive adhesive, such as a water soluble white glue, is used. As the endless core is belt driven down the line, it reaches a second adhesive applicator where a continuous adhesive stream is applied to the outer surface of the core after which a continuous strip of the cover material, such as polyester, is helically wound on to the core where it is secured by the adhesive. All that remains is to cut the resulting endless roller down to usable sizes, which is usually accomplished in two steps, first using a fly away cutter to cut, e.g., 64 inch stock, and then using a recutter to cut the stock into lengths of, e.g., seven or nine inches. The rollers thus formed may not be reused, as the adhesive which binds the core and secures the cover to the core is soluble in paint solvents, and consequently any attempt to clean the roller leads to unravelling of the core and separation of the core from the cover.
If reusable rollers are desired, phenolic impregnated paper strips are substituted for the chipboard strips in the process described above, and a thermosetting glue is used for securing the core. Thereafter, the core is heated in a multi-stage infrared heater, after which a hot melt glue is applied to the core's outer surface. The rollers are then completed as before, i.e. by helically winding the fabric cover on to the core and then cutting the resulting endless roller into usable lengths. The obvious drawback of reusable cores formed in this manner is that they require a longer assembly line, due to the need of a heater, and because the phenolic must be heated to a predetermined temperature, there is an obvious trade off between the number of heater stages and the speed of the line. Moreover, while the resulting rollers are termed reusable because they do not separate when placed in paint solvents, prolonged exposure to such solvents, e.g. about two days, does result in separation.
Another reusable roller is disclosed in U.S. Pat. No. 4,692,975 issued to Garcia. Rather than using helically wound strips to form the core, the Garcia roller is formed using a core comprised of preformed thermoplastic (e.g. polypropylene) tubular stock. With the core mounted on a rotating spindle, a movable carriage mounted at an angle to the spindle feeds a continuous strip of fabric, the carriage moving parallel to the spindle in timed relation to its rotation so that the fabric strip is wound on the plastic core in a tight helix. Also mounted to the movable carriage is a heat source for heat-softening the thermoplastic core just in advance of the point where the fabric strip is applied, such that the fabric is bonded to the core as it is wound thereon. One advantage of the roller disclosed in the Garcia patent is that it is reusable, as the bond formed between cover and core is a strong one not subject to separation from exposure to paint solvents. Another advantage is that the manufacturing process does not require the application of an adhesive to bond the cover to the core. There are, however, drawbacks. For one, while prior art techniques use rolls of, e.g., chipboard or paper, the Garcia process requires preformed thermoplastic tubular cores which are considerably bulkier than rolls, more expensive to transport, and more difficult to handle. Another drawback is the anticipated speed limit of the Garcia process dictated by the necessity that the heater, which advances along the core just in front of the fabric strip, move slow enough to insure softening of the thermoplastic core, in the absence of which the fabric cover will not bond.